Session: 09-01-01 Wind Turbine Aerodynamics and Control

Submission Number: 152892

Sensitivity of Floating Wind Turbine Motions to Stable Boundary Layer Wind Profiles 

Atmospheric stability influences the structural response of wind turbines through effects on both the mean wind profile and turbulence characteristics. Commonly used surface layer wind profile models, such as the logarithmic and power laws, are limited in their ability to account for the full impact of atmospheric stability. Especially in stable atmospheres, where the surface layer is shallow, these conventional models tend to overestimate mean wind speeds at higher altitudes relevant to modern wind energy applications. Moreover, stable atmospheric conditions are frequently characterized by negative shear regions, such as low-level jets, and by non-negligible wind veering. Both shear and veer in the wind profile can significantly affect the structural response of wind turbines, particularly for large rotor systems. More sophisticated models are thus needed to accurately represent stable boundary layer wind profiles and reduce uncertainties in wind turbine response simulations. 
This study examines the sensitivity of a floating wind turbine's global motions to stable wind profiles generated by different profile models. Conventional logarithmic surface layer profiles are compared with two more advanced approaches. One of these models extends the logarithmic profile to the boundary layer height, incorporating a turbulent length scale as a function of height and atmospheric stability. The second model combines Monin-Obukhov similarity theory with Ekman boundary layer flows, utilizing a self-consistent geostrophic drag law and an equilibrium boundary layer height model. This approach allows for the estimation of both wind velocity and direction profiles in neutral and stable conditions, including the presence of a low-level jet.   
The wind profiles are used to create turbulent wind fields as inputs for dynamic response simulations, carried out for the IEA 15 MW reference turbine on the VolturnUS-S floating reference platform. The study focusses on the semi-submersible platform’s rigid body motions and their sensitivity to the given wind profiles. The response simulations highlight the floater motions’ sensitivity to atmospheric stability, negative shear, and wind veering, emphasizing the importance of using advanced wind profile models for the efficient design of wind turbine components.

Presenting Author: Lennart Vogt University of Stavanger (UiS)

Presenting Author Biography: I am a PhD candidate at the University of Stavanger in Norway, focussing on the effects of atmospheric stability on the response of floating wind turbines. I hold an M.Sc. in Wind Energy Engineering from Flensburg University of Applied Sciences.